They then fed the fish fluorescent pellets and found that the fish had problems discarding food waste and were constipated.

Professor Bernier said this is the first time that researchers have linked a definitive cause of autism to a genetic mutation.

Although just 0.5 per cent of all children have the kind of autism related to the CHD8 mutation, he said that there are lots of implications from the study.

A team of researchers disrupted the CHD8 gene in the zebra fish, (pictured) which developed large heads and wide set eyes. They then fed the fish fluorescent pellets and found that the fish had problems discarding food waste and were constipated

‘This will be a game changer in the way scientists are researching autism,’ Professor Bernier said.

The results could pave the way for a ‘genetics-first approach’ that could uncover hundreds more genetic mutations and lead to genetic testing, he explained.

Genetic testing could be offered to families as a way of guiding them on what to expect and how to care for their child.

Currently autism is diagnosed by doctors examining and assessing a child’s behaviour.

In the short term, Professor Bernier said that clinicians can pay attention to the small population with this CHD8 mutation and provide targeted treatment.

Autism has already been linked to different types of genetic events. The most commonly researched genetic events associated with autism are chromosomal re-arrangements, called ‘copy number variations,’ in which a chunk of chromosome is copied or deleted.

But no one rearrangement affects more than one per cent of all autism cases and there is no definitive link between the rearrangement and autism.

The CHD8 gene mutation is the first gene mutation to show a ‘very strong penetrance’ – or link – to a certain subtype of autism.

…AND AN APP COULD DIAGNOSE CHILDREN WITH AUTISM

Scientists have developed an app that can detect signs of autism as well as a trained expert.

They said in May that the software is also more accurate than medics who are not autism experts

The researchers, from Duke University, in North Carolina, believe the technology could eventually be placed in schools as a way of screening children for autism.

They believe this would be particularly beneficial as it is known children with autism develop fewer symptoms if they are diagnosed early.

The software works by tracking and recording infants’ activity during filmed autism screening tests.

Experts currently use behavioural tests to identify autism in very young children, such as shaking a toy from side to side and seeing how long it takes for a child’s attention to shift in response to the changing stimulus.

The new programme provides automatic measurements of reaction times down to tenths of a second.

‘The great benefit of the video and software is for general practitioners who do not have the trained eye to look for subtle early warning signs of autism,’ said Amy Esler, an assistant professor of paediatrics and autism researcher at the University of Minnesota, who participated in some of the trials.

‘The software has the potential to automatically analyse a child’s eye gaze, walking patterns or motor behaviours for signs that are distinct from typical development.